Search

Herein, the influence of the Ga–OH bond at the GaN surface on the electrical characteristics of the SiO2/GaN metal-oxide semiconductor structure is investigated. The GaN surface is modified by three different surface treatments (O2 annealing, wet annealing, and ultraviolet [UV]/O3 treatment). The Ga–OH bond is evaluated by X-ray photoelectron spectroscopy and characterized by capacitance–voltage (CV) measurements and a positive bias stress test. Increasing the ratio of Ga–OH bonds at the SiO2/GaN interface decreases the net fixed charge at the SiO2/GaN interface in the CV measurements and increases the voltage shift in the stress test. Therefore, the Ga–OH bond at the SiO2/GaN interface develops a negative charge and behaves as an electron trap. The undesirable influence of the Ga–OH-related traps is reduced by low-temperature annealing.

The electrical properties of SiO2/GaN metal-oxide-semiconductor capacitors with different SiO2 thicknesses are evaluated before and after postmetallization annealing (PMA). The distribution of charges in bulk SiO2 and the SiO2/GaN interface is estimated by analyzing the electrical properties. It is revealed that the net effective charges (Nf) tend to increase with decreasing SiO2 thickness before PMA. This indicates that the negative bulk charges are present uniformly, and the positive interface charges exist locally near the interface. In the sample after PMA, Nf tends to decrease with decreasing SiO2 thickness at the thin SiO2 region (

Al2O3/TiO2 double layer anti-reflection coating (ARC) film formed by spray pyrolysis was introduced for monocrystalline silicon solar cells as the nonvacuum processing method. The thickness of the Al2O3 layer and TiO2 compact layer was controlled by the volume of deposited precursor solution and confirmed by ellipsometry and scanning electron microscope. The average photovoltaic properties of photocurrent density (Jsc), the open-circuit photovoltage (Voc), the fill factor (FF), and the photo energy conversion efficiency (η) were 37.0 mA/cm2, 590 mV, 0.712, and 15.5%, respectively. A significant improvement on Jsc and η could be confirmed owing to the Al2O3/TiO2 ARC. According to the results of Fourier transform infrared (FTIR) spectroscopy and optical simulation with modeling for the reflectance properties, it was confirmed that C-H-based organics remained after the deposition of thin films.

We designed and mass-produced a versatile protein supramolecule that can be used to manufacture a highly efficient dye-sensitized solar cell (DSSC). Twelve single-walled carbon-nanotube (SWNT)-binding and titanium-mineralizing peptides were genetically integrated on a cage-shaped dodecamer protein (CDT1). A process involving simple mixing of highly conductive SWNTs with CDT1 followed by TiO2 biomineralization produces a high surface-area/weight TiO2 -(anatase)-coated intact SWNT nanocomposite under environmentally friendly conditions. A DSSC with a TiO2 photoelectrode containing 0.2 wt % of the SWNT-TiO2 nanocomposite shows a current density improvement by 80% and a doubling of the photoelectric conversion efficiency. The SWNT-TiO2 nanocomposite transfers photon-generated electrons from dye molecules adsorbed on the TiO2 to the anode electrode swiftly.

We have investigated thermal distribution of an amorphous InSnZnO thin-film transistor (TFT) under voltage stress by using thermal imaging system. To clarify an influence of only self-heating phenomenon on reliability, we have focused on a channel scale dependence of heating. As the result, heating effect were strongly depended on channel scale and showed two types of dependences on channel length and width. When positive bias stress was applied to TFT, severe threshold voltage shift and high heating temperature were observed for wider TFT. Moreover, reliability under voltage stress was seems to be affected by accumulation of heating in wider TFT. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper briefly reviews the characterizations of Al2O3 gate dielectric deposited by plasma-assisted atomic layer deposition (PA-ALD) on n-GaN. We report on insulating and physical properties of PA-ALD Al2O3 film from I-V characteristics of metal-insulator-semiconductor (MIS) diodes and analysis of X-ray photoelectron spectroscopy (XPS), respectively. Compared to Al2O3 film deposited by thermal ALD method, the PA-ALD Al2O3 film exhibited higher breakdown field and several orders of magnitude lower leakage current density. Analysis of the current conduction mechanism reveals that the gate leakage current of PA-ALD Al2O3/n-GaN MIS diode consisted of Schottky emission (SE) and Fowler-Nordheim tunneling (FNT). In contrast, it is suggested that trap-assisted tunneling (TAT) mechanism was dominant in the gate leakage of T-ALD Al2O3 sample at the middle field range. From the XPS analysis, the band gap of PA-ALD Al2O3 was estimated about 6.7 eV. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)